don't spoil me but I suspect that Diina is actually the goddess herself, I mean there're hints everywhere especially when she interrupted the demon king's speech.
Is this the prologue of Kumoko chan? I mean the story is Hero and Demon lord cooperate to destroy the system, therefore the dimension distorted and killed students in the whole classroom.
one thing I hate about Korean comics, They dropped bomb after bombs without giving reader a rest or the moment of relaxation. They did give characters some rest of course but we readers just happen to know more than MC and how can we rest when we're expecting something to happen ?